Systemic lupus erythematosus (SLE) is a chronic autoimmune disease of unknown etiology that is characterized by the presence of a wide spectrum of clinical manifestations and serologic abnormalities. Genetic, environmental, hormonal and immunological factors have been implicated in the etiopathogenesis of SLE. The prevalence of most clinical features, serologic abnormalities and genetic markers varies widely among different races or ethnic populations. Except for a few epidemiological studies, there is no data on SLE in Puerto Ricans. Preliminary studies performed at the Ramon Ruiz Arnau University Hospital reveal significant difference in clinical and immunologic characteristics of SLE in Puerto Ricans as compared to other ethnic populations. The overall objective of the proposed research is to gain a better understanding of SLE in Puerto Ricans. Approximately 100 Puerto Ricans with SLE will be recruited and followed prospectively in the clinical research clinic. A comprehensive data base of clinical features such as clinical manifestations, treatments, exacerbations, hospitalizations, complicating infections, and comorbid conditions will be established. A thorough immunologic analysis will be performed for each patient. The specificities of Human Leukocyte Antigen (HLA) HLA-DR and HLA-DQ will be determined in SLE patients and compared to normal individuals. Conventional and exploratory statistical analysis with the collected clinical, immunologic and genetic data will be performed. The result of this study will provide valuable and novelle information of a still unexplored ethnic population with SLE. It will allow to provide better care and management to Puerto Rican SLE patients according to their own and distinctive clinical and immunogenetic characteristics.